Table S1.
Demographics of mothers and puppies in the study
| Litter | Litter size | Puppies included in analyses | Mother’s breed | Father’s breed | Puppies’ breed | Labrador Retriever, % | Coded puppy breed |
| Della | 6 | 5 | Labrador Retriever | Golden Retriever | Lab-Golden cross | 50 | Labrador Retriever |
| Lizzie | 9 | 5 | Golden Retriever | Golden Retriever | Golden Retriever | 0 | Golden Retriever |
| Dagmar | 8 | 6 | German Shepherd | German Shepherd | German Shepherd | 0 | German Shepherd |
| Dori | 5 | 2 | Golden Retriever | Labrador Retriever | Lab-Golden cross | 50 | Golden Retriever |
| Lolly | 2 | 0 | German Shepherd | German Shepherd | German Shepherd | 0 | German Shepherd |
| Dotty | 2 | 1 | Golden Retriever | Labrador Retriever | Lab-Golden cross | 50 | Golden Retriever |
| Onyx | 8 | 5 | Labrador Retriever | Labrador Retriever | Labrador Retriever | 100 | Labrador Retriever |
| Maude | 9 | 5 | Labrador Retriever | Labrador Retriever | Labrador Retriever | 100 | Labrador Retriever |
| Ayesha | 10 | 7 | Labrador Retriever* | Labrador Retriever | Lab-Golden cross × 3 | 87.5 | Labrador Retriever |
| Foxy | 7 | 5 | German Shepherd | German Shepherd | German Shepherd | 0 | German Shepherd |
| Toffee | 6 | 5 | Labrador Retriever | Labrador Retriever | Labrador Retriever | 100 | Labrador Retriever |
| Carey | 8 | 5 | Labrador Retriever | Labrador Retriever | Labrador Retriever | 100 | Labrador Retriever |
| Aura | 7 | 6 | German Shepherd | German Shepherd | German Shepherd | 0 | German Shepherd |
| Naomi | 8 | 6 | Labrador Retriever* | Labrador Retriever | Lab-Golden cross × 3 | 87.5 | Labrador Retriever |
| Omega | 8 | 7 | Golden Retriever | Golden Retriever | Golden Retriever | 0 | Golden Retriever |
| Lea | 6 | 6 | German Shepherd | German Shepherd | German Shepherd | 0 | German Shepherd |
| Leah | 5 | 3 | German Shepherd | German Shepherd | German Shepherd | 0 | German Shepherd |
| Paris | 4 | 2 | German Shepherd | German Shepherd | German Shepherd | 0 | German Shepherd |
| Elise | 9 | 8 | German Shepherd | German Shepherd | German Shepherd | 0 | German Shepherd |
| Xyris | 7 | 6 | Labrador Retriever | Labrador Retriever | Labrador Retriever | 100 | Labrador Retriever |
| Lisa | 4 | 3 | German Shepherd | German Shepherd | German Shepherd | 0 | German Shepherd |
*
These dogs are Labrador-Golden crosses × 2, meaning their mothers were 50%-50% Labrador-Golden crosses and their sires were 100% Labrador Retrievers, making them 75% Labrador Retriever. Thus, these dogs were classified as Labrador Retrievers.